Solar wind dependence of electric conductances and currents in the auroral zone
Solar wind dependence of electric conductances and currents in the auroral zone
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极光区电导和电流对太阳风的依赖性
DOI：
10.1016/j.jastp.2017.07.006
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发表时间：
2017
影响因子：
1.9
通讯作者：
and K. Kauristie
中科院分区：
文献类型：
--
作者：
Sergeeva;V.;N. Stepanova;Y. Ogawa;S. Kakic;and K. Kauristie
基于斯堪的纳维亚半岛 EISCAT 非相干散射雷达和 IMAGE 磁力计长达 20 年的观测数据库，我们统计研究了暗夜侧极光区的电离层电导变化。我们重点关注降水引起的电导与当地等效电流和全球 AL 指数变化的关系，以及它们对太阳风（SW）参数的依赖性。就成对相关性而言，AL 指数以及 Pedersen 和霍尔电导（Σ P 和 Σ H）的主要 SW 驱动因素是 SW 合并电场（例如，用 Kan-Lee 函数 E k l 表征）和太阳风速度 V s w。这些软件驱动程序的相对重要性各不相同。尽管 E k l 是 AL 指数的主要驱动因素，但 V sw 对电导的作用有所增加，因此它超过了 E k l 作为霍尔电导的主要驱动因素。从数量上讲，这种依赖性表示为 Σ H=(7.7* V+ 1.75* V 2)+(5.7* E− 0.86* E 2)− 6.1 西门子，其中 E 和 V 分别是用 < E k l>= 0.79 mV/m 和 < V s w>= 429 km/s 标准化的 E k l 和 V s w。然而，V s w 的最强影响是针对霍尔-佩德森电导比 R H P= Σ H/Σ P 观察到的，表明太阳风速度对电子加速的控制。从物理上讲，通电是导致电导值较大的主要因素。在夜间，局部等效电流主要受局部霍尔电导 (CC= 0.78) 控制，并且活跃期间大部分等效电流的增加是由于电导率的变化。从这个意义上说，活动期间的 AL 指数变化是由霍尔电导变化控制的，而霍尔电导变化在很大程度上是由磁层电子加速过程控制的。
Based on 20 years-long data base of EISCAT incoherent scatter radar and IMAGE magnetometer observations in Scandinavia, we investigate statistically the ionospheric conductance variations in the dark nightside auroral zone. We focus on the relationship of precipitation-caused conductances with the variations of local equivalent current and global AL index, as well as on their dependence on the solar wind (SW) parameters. In terms of paired correlation, the main SW drivers for AL index and for the Pedersen and Hall conductances (Σ P and Σ H) are the SW merging electric field (characterized, eg, with the Kan-Lee function, E k l) and the solar wind velocity V s w. The relative importance of these SW drivers varies. Whereas E k l is the main driver of AL index, the role of V s w increases for the conductances so that it outruns the E k l as the main driver for the Hall conductance. Quantitatively this dependence is represented as Σ H=(7.7* V+ 1.75* V 2)+(5.7* E− 0.86* E 2)− 6.1 Siemens, where E and V are E k l and V s w normalized with< E k l>= 0.79 mV/m and< V s w>= 429 km/s. The strongest influence of V s w is, however, observed for the Hall-to-Pedersen conductance ratio R H P= Σ H/Σ P, indicating solar wind velocity control of the electron acceleration. Physically the energization is a major factor which contributes to the large conductance values. On the nightside, local equivalent currents are significantly controlled by the local Hall conductance (CC= 0.78) and most of the equivalent current increase during active periods is due to the conductivity change. In that sense the AL index variations during active times are controlled by the Hall conductance variations which, to a large extent, are controlled by the processes of magnetospheric electron acceleration.